Lauda Air Flight 004 was an international passenger flight using a Boeing 767-300ER that crashed on 26 May 1991 due to an un-commanded thrust reverser deployment of the No.1 engine in mid-flight, killing all 213 passengers and the 10 crew members on board. To date, it remains the deadliest aviation accident involving a Boeing 767 and the deadliest on Thai soil. The crash also marked the aircraft type's first fatal incident and first hull-loss.